An Implementation of Axisymmetry in Numerical Relativity Using a Multipatch Scheme

With the observation of a kilonova signal following the detection of the binary neutron star merger GW170817, the need for an extended duration simulation of the post-merger environment has become important in order to determine the effects of the stability of the remnant by secular processes on any observed signals. In order to extend simulation times in the Spectral Einstein Code (SpEC), we have developed a modification to SpEC's multipatch coordinate transformation implementation to allow for easily running a post-merger simulation in axisymmetry without the need to explicitly rewrite evolved equations in an axisymmetric form. Several tests using simple equilibrium systems with magnetic fields, neutrino transport, and viscosity have shown the viability of this method and demonstrated a significant decrease in required computational resources versus a full 3D simulation.